The present invention relates to a brush device for a direct current machine such as a starter motor.
FIGS. 4A and 4B show a front view and a side view of a first conventional brush device. In FIGS. 4A and 4B, a reference numeral 1 designates a commutator of a direct current machine, 4, a brush holding frame, for instance, formed by a synthetic resin, which is provided with pairs of brush accommodating portions 4a and 4b which are open at end portions thereof and at inner peripheral portions thereof in the radial direction. The brush accommodating portions 4a accommodate positive brushes 5a and brush springs 8, and the brush accommodating portions 4b accommodate negative brushes 5b and the brush springs 8. In the brush holding frame 4, a pair of protruded portions 4c are extended in the radial direction, on the side of an end face of which a stepped stopper portion 4d is formed, and a pair of stopper protrusions 4e are formed at intermediate positions with respect to the peripheral direction of the pair of protruded portions 4c. As shown by a chain line in FIG. 4A, an insulation plate 12 touches an end face of the brush holding frame 4, engages with the stepped stopper portion 4d and the stopper protrusions 4e, thereby positioning the insulation plate 12 vertically and horizontally, and covers the open portions of the end portions of the brush accommodating portions 4a and 4b. FIG. 6 is a front view of the insulation plate 12. FIGS. 5A and 5B are sectional diagrams of the brush accommodating portion 4a and the stopper protrusion 4e of FIG. 4A.
In FIGS. 4A and 4B, the insulation plate 12 is pinched and fixed to the protruded portions 4c by a pair of attaching pieces 9a and 9b made of a metallic material. Lead wires 6a are extended from the pair of brushes 5a and are connected to a lead wire 7. The lead wire 7 is fitted with a grommet 11 and connected to a terminal 10 at an end thereof. Lead wires 6b are extended from the pair of brushes 5b and connected to the attaching piece 9b.
As shown in FIG. 4B, the brush device integrated as above is mounted on an inner face of an end portion of a rear bracket 2 (shown by a chain line) of a starter motor by screwing screws 3 into tapped holes 9c thereby fixing the attaching pieces 9a and 9b. The rear bracket 2 fixed with the brush device is connected to a front bracket (not shown) by through bolts through a yoke (not shown) of the starter motor. The brushes 5a and 5b are press-contacted to the commutator (shown by a chain line) for flowing current.
In the above conventional brush device, the insulation plate 12 is stopped of its relative motion vertically and horizontally by the stepped stopper portion 4d of the brush holding frame 4 and the stopper protrusions 4e, and is pinched by the attaching pieces 9a and 9b. However, there is a play in the assembly due to working tolerances of the respective corresponding parts. Especially, although the insulating plate 12 is pinched by the attaching pieces 9a and 9b only at the two places on the top side and on the bottom side thereof, the left and right portions thereof float from the end portions of the brush holding frame 4 and vibrate by an outside vibration. As a result, in the insulating plate 12, wear is promoted at the engaging portions by this vibration, the play is magnified, a mismatch is caused and a trouble is brought about in the receiving operation of the brushes 5a and 5b at sides thereof in the width direction.
FIGS. 12A and 12B show a front view and a side view of a second conventional brush device. In FIGS. 12A and 12B, a reference numeral 101 designates a commutator of a direct current machine, 104, a brush holding frame, for instance, formed by a synthetic resin, which is provided with pairs of brush accommodating portions 104a and 104b which are open at end portions thereof and at inner peripheral portions thereof in the radial direction. The brush accommodating portions 104a accommodate positive brushes 105a and brush springs 108, whereas the brush accommodating portions 104b accommodate negative brushes 105b and the brush springs 108. In the brush holding frame 104, a pair of protruded portions 104c are extended in the radial direction. As shown in FIG. 12A by a chain line, an insulation plate 112 touches an end face of the brush holding frame 104, engages with a stepped stopper portion 104d and covers the open portions at the end portions of the brush accommodating portions 104a and 104b. FIG. 13 is a sectional diagram showing the brush accommodating portion 104a of FIG. 12A.
In FIGS. 12A and 12B, the insulation plate 112 are pinched and fixed to the protruded portions 104c by a pair of attaching pieces 109a and 109b made of a metallic material. Lead wires 106a are extended from the pair of brushes 105a and connected to a lead wire 107. The lead wire 107 is fitted with a grommet 111 and is connected to a terminal 110 at an end thereof. Furthermore, lead wires 106b are extended from the pair of brushes 105b and connected to the attaching pieces 109b. FIG. 14 is a sectional diagram taken along a line A.sub.8 --A.sub.8 of FIG. 12A. A numeral 104f designates a screw accommodating hole of an attaching screw 103 (refer to FIG. 12B) provided at the protruded portion 104c of the brush holding frame 104. A numeral 104i designates slots provided at the protruded portions 104c for passing burring portions which are provided with tapped holes 109c of the attaching pieces 109a and 109b.
As shown in FIG. 12B, the brush device integrated as above, is fixed to an inner face of an end portion of a rear bracket 102 (shown by a chain line) of a starter motor, by screwing the screws 103 into the tapped holes 109c thereby fixing the attaching pieces 109a and 109b. The rear bracket 102 fixed with the brush device is connected to a front bracket (not shown) by through bolts through a yoke (not shown) of the starter motor. The brushes 105a and 105b are press-contacted to the commutator 101 (shown by a chain line) for flowing current.
In the above conventional brush device, the attaching pieces 109a and 109b are only fixed by pinching them to the protruded portions 104c of the brush holding frame 104. Therefore, when the direct current machine receives a vibration, the brush holding frame 104 and the attaching pieces 109a and 109b vibrate separately, wear is generated at the fitting portions for the both, a play is generated therebetween, destruction is caused and the contact operation of the brushes 105a and 105b to the commutator 1 is hampered. Furthermore, the positioning accuracy of the attaching pieces 109a and 109b with respect to the protruded portions 104c of the brush holding frame 104, is low and the operation of attaching the brush device to the rear bracket is difficult.
FIGS. 18A and 18B are a front view and a side view of a third conventional brush device. In FIGS. 18A and 18B, a reference numeral 201 designates a commutator of a direct current machine, and 204, a brush holding frame, for instance, formed of a synthetic resin, which is provided with pairs of brush accommodating portions 204a and 204b which are open at end portions thereof and at inner peripheral portions thereof in the radial direction. The brush accommodating portions 204a accommodate positive brushes 205a and brush springs 208, whereas the brush accommodating portions 204b accommodate negative brushes 205b and the brush springs 208. In the brush holding frame 204, a pair of protruded portions 204c are extended in the radial direction. As shown in FIG. 18A by a chain line, an insulation plate 212 touches an end face of the brush holding frame 204, engages with a stepped stopper portion 204d and covers the open portions at the end portions of the brush accommodating portions 204a and 204b. FIG. 19 is a sectional diagram of the brush accommodating portion 204a of FIG. 18A. In FIGS. 18A and 18B, the insulation plate 212 is pinched and fixed to the protruded portions 204c by a pair of attaching pieces 209a and 209b made of a metallic material. Lead wires 206a are extended from the pair of brushes 205a and are connected to a lead wire 207. The lead wire 207 is fitted with a grommet 211, and is connected to a terminal 210 at an end thereof. Lead wires 206b are extended from the pair of brushes 205b and are connected to the attaching piece 209b.
As shown in FIG. 18B, the brush device integrated as above, is mounted on an inner face of an end portion of a rear bracket 202 (shown by a chain line) of a starter motor, by screwing screws 203 into tapped holes 209c thereby fixing the attaching pieces 209a and 209b. The rear bracket 202 attached with the brush device is connected to a front bracket (not shown) by through bolts through a yoke (not shown) of the starter motor. The brushes 205a and 205b are press-contacted to the commutator 201 (shown by a chain line) for flowing current.
In the U-shaped attaching pieces 209a and 209b of the conventional brush device, as shown in FIG. 20A by a side sectional diagram and FIG. 20B by a bottom view, when a tapping is performed to form the tapped holes 209c at first straight portions thereof, since a space between the first straight portion and a second straight portion thereof is small, a front end of a tap 215 touches the second straight portion, and therefore, a complete tapping can not be performed. Therefore, several kinds of special taps are to be prepared and exchanged to successively work out a complete screw out of the incomplete screw and the machining thereof is difficult. Furthermore, when the length of a female screw is shortened to avoid the above problem, the number of the thread ridges screwed in the tapped holes becomes small and the thread ridges are crushed by the screwing.
FIGS. 24A and 24B show a front view and a side view of a fourth conventional brush device. In FIGS. 24A and 24B, a reference numeral 301 designates a commutator of a direct current machine, and 304, a brush holding frame, for instance, formed by a synthetic resin, which is provided with pairs of brush accommodating portions 304a and 304b and which are open at end portions thereof and at inner peripheral portions thereof in the radial direction. The brush accommodating portions 304a accommodate positive brushes 305a and brush springs 308, whereas the brush accommodating portions 304b accommodate negative brushes 305b and the brush springs 308. In the brush holding frame 304, a pair of protruded portions 304c are extended in the radial direction. As shown in FIG. 24A by a chain line, an insulation plate 312 touches an end face of the brush holding frame 304, engages with a stepped stopper portion 304d and covers the open portions of the end portions of the brush accommodating portions 304a and 304b. FIG. 25 is a sectional diagram showing the brush accommodating portion 304a of FIG. 24A.
In FIGS. 24A and 24B, the insulation plate 312 is pinched and mounted to the protruded portions 304c by a pair of attaching pieces or clamps 309a and 309b. Lead wires 306a are extended from the pair of brushes 305a and are connected to a lead wire 307. The lead wire 307 is fitted with a grommet 311 and is connected to a terminal 310 at an end thereof. Lead wires 306b are extended from the pair of brushes 305b and are connected to the attaching piece 309b.
The integration of the brush device assembled as above to a motor is carried out as follows. First, a front bracket of the starter motor is placed in a standing setup of a motor, on which a yoke portion is placed. The armature is inserted into the assembly of the front of the yoke portion with the commutator 301 placed on the top side thereof. The brush device is tentatively placed at the periphery of the commutator 301. A rear bracket 302 is placed on the yoke from the top side. Through bolts 316 are passed through thereby tightening and connecting the rear bracket 302 to the front bracket. Next, screws 303 are screwed into tapped holes 309c of the attaching pieces 309a and 309b from the top side of the rear bracket 302, thereby fixing the brush device and press-contacting the brushes 305a and 305b to the commutator 301.
In the above conventional brush device, as for the mounting thereof, the positioning of the attaching pieces 309a and 309b of the brush device in the peripheral direction with respect to the positions of the screws 303 of the rear bracket 302, is difficult and takes much time.